Current advanced radar systems favor highly integrated designs in order to reduce cost and to aid in the manufacturability of complex systems. As a result, tile architecture antenna designs are highly desirable implementations. However, one drawback to tile architecture antenna designs is the bandwidth of such antennas. Another drawback is that driving a tile architecture antenna with a differential signal from an integrated circuit (IC) requires a single-ended to double-ended balun. Most antennas in tile architectures require a considerable height or length in the “Z” direction to provide the required bandwidth. This inherently limits the integration of a tile architecture antenna design into multiple components: 1) the antenna, 2) the balun, and 3) the electronics.
Low profile wideband antennas are commonly desired for conformal and highly integrated antenna designs. Most wideband antennas (e.g., notch antenna, Vivaldi antenna) require some amount of height in the Z-direction in order to provide the necessary bandwidth. So called “bowtie” antennas are also able to provide a large amount of bandwidth and may require less height in the Z-direction. But, in order to be used in a practical array, these bowtie antennas require a ground plane in order to direct radiation in one hemisphere. This requires that the bowtie antenna be a quarter wavelength (λ/4) from the ground plane. This requirement severely limits the bandwidth.
There are limited options for planar antenna designs with wide bandwidth that can be fabricated with a simple printed circuit board (PCB) process. One solution that is not planar and involves an extended fabrication process is the vivaldi “egg crate” array. However, this requires a complex interface to the radio frequency (RF) electronics to sum array elements in cross dimensions or to add dual polarization capability. Also, the required height in the Z-direction to obtain broadband performance prevents a low profile solution necessary for many applications. Implementations like the vivaldi with antenna designs that require card like interfaces are difficult to integrate and fabricate. At some point, the antenna design must transition to a planar substrate and this complicates integration by requiring the manufacturing process to join two or more physically separated sections.
If the antenna were itself planar and made using traditional PCB manufacturing processes, this would allow for a highly integrated design that is simple to fabricate and manufacture. Prior art publications have disclosed that placing a bowtie antenna over an electromagnetic band gap (EBG) material allows for the bowtie antenna to keep its impedance bandwidth while preserving the pattern performance in that band. But, while the EBG material satisfies the Z (height) condition, the additional requirement of needing a balun adds complications to the design. Baluns proposed in conventional designs require micro-strip Wilkinson designs or twin lead transmission lines along the Z-direction of the substrate.
Also, given a tightly packed array, a planar solution for a balun is not always possible. Currently, the industry solution is to develop a planar balun and then orient the balun perpendicular to the dipole in order to feed it. However, this creates considerable mechanical issues and may cause reliability and repeatability issues. PCB-mounted differential antennas need an integrated balun that conforms to current PCB processes and leaves a small footprint in order to allow for maximum area to accommodate multiple traces and components.
Therefore, there is a need in the art for an improved antenna designs. In particular, there is a need for improved planar antenna systems that may be implemented using an antenna tile architecture.